The overall purpose of this research proposal is to examine the role of the limbic system in hypothalamic aggression. The first phase of the research project attempts to determine how the limbic system and related structures modulate quiet biting and affective attack behavior elicited by electrical stimulation of the hypothalamus. The principal paradigm involves presentation of paired trials of single (hypothalamic) and dual (limbic plus hypothalamic) stimulation. Differences in response latency between paired trials of single and dual stimulation provide the basis for determining the effects of limbic stimulation upon hypothalamic aggression. The limbic structures thus far considered include the hippocampus, septal area, cingulate gyrus, pyriform cortex, and prefrontal cortex. In this proposal structures to be studied include the substantia innominata and adjacent regions. A second phase of this project will attempt to determine the origin and distribution of the fibers of the septal area in the cat which presumably relate to the control of attack behavior. A third phase will attempt to determine the neurophysiological relationships between the substantia innominata and the various component nuclear groups of the amygdala.